1. Field of the Invention
The present invention relates generally to bumpers for motor vehicles and, more specifically, to an energy-absorbing bumper system for a motor vehicle.
2. Description of Related Art
All motor vehicles have bumpers at the front and rear ends of the motor vehicle. Typically, the bumpers include a bumper beam, which provides protection against damage and injury in case of a collision involving the motor vehicle. The bumper beams at the front and rear ends of the motor vehicle body extend transversely with respect to the longitudinal axis of the motor vehicle body. At the front and typically rear ends of the motor vehicle body, the bumper beams are secured to a pair of rails, which connect the bumper beams to the motor vehicle body. The bumper beams are secured to the ends of the rails. The rails extend longitudinally and are spaced apart at the front and rear ends of the motor vehicle body. The bumper beams are typically connected to the rails by end brackets. It is often difficult to fit these end brackets in the space available in the vicinity of the bumper beams as well as to properly mate the end brackets with the bumper beams and rails. Generally, the end brackets used in bumpers are heavy structures that rigidly connect the bumper beams and rails. Their size and weight makes them expensive to manufacture. Additionally, the bumper beams, end brackets, and rails are typically specifically designed as a distinct system. Thus, for example, the end brackets of one type of bumper are not generally suitable for use in another bumper used on a different model of motor vehicle.
Numerous bumper systems are known in the art for connecting a bumper beam with a set of rails extending from a motor vehicle body. For example, U.S. Pat. No. 6,485,072 to Werner et al. discloses a bumper system for a motor vehicle that includes a bumper beam and an energy absorber disposed between the bumper beam and bumper fascia covering the bumper beam. The bumper beam is connected directly to the rails extending from the motor vehicle body. The connection between the bumper beam and rails is a rigid connection, for example, consisting of welds or mechanical fasteners. The energy absorber is made of a deformable material such as foam.
U.S. Pat. No. 6,338,510 to Kanamori et al. discloses a bumper system for a motor vehicle that includes pivotal end brackets for joining a bumper reinforcement member (i.e., bumper beam) to a pair of rails extending from the motor vehicle body. The bumper brackets each have a boss defining a vertical hole that receives a bolt, which connects the bumper beam to the rail. The bolt and boss arrangement establishes a pivotal connection between the bumper beam and rail. The pivotal connection between these elements allows the bumper brackets to rotate or pivot inward a given angular range toward a central longitudinal axis of the motor vehicle body for redirecting impact forces during a collision.
U.S. Pat. No. 6,334,638 to Yamamuro et al. discloses an attachment structure for connecting a bumper beam to the ends of a pair of rails in a motor vehicle. The attachment structure includes a pair of bumper stays or brackets each having an impact-absorbing member, which deforms to absorb impact energy during a collision. The bumper stays or brackets are formed as a combined unit, each incorporating the impact-absorbing member and a rigid holding member supporting the impact-absorbing member. The bumper beam is mounted directly to the impact-absorbing members.
U.S. Pat. No. 6,113,164 to Setina discloses an auxiliary push bumper for a motor vehicle. The push bumper is clamped to the original bumper by brackets attached to bumper guards on the push bumper. The push bumper is made of a plurality of sections made of extruded aluminum that are attached removably to the bumper guards for easy repair and maintenance. The auxiliary push bumper is specifically adapted for use on police vehicles and the like.
U.S. Pat. No. 6,042,163 to Reiffer discloses a motor vehicle bumper having a bumper beam. The bumper beam is connected to the rails of the motor vehicle body by one-piece end brackets. The end brackets are attached and fit over opposing ends of the bumper beam. The end brackets are tubular and include overlapping flanges that allow the end brackets to be adjusted to the ends of the bumper beam. Stays are welded to and extend from the end brackets for attaching the end brackets to the rails of the motor vehicle body.
U.S. Pat. No. 4,488,745 to Stokes discloses a plastic support for attaching a plastic bumper to the metal frame of a motor vehicle body. The plastic support is comprised of a metal pad having an attachment device for attaching the metal pad to the metal frame of the motor vehicle body. The metal pad is embedded in a molded plastic matrix except where the metal pad is to be attached to the frame of the motor vehicle body.
U.S. Pat. No. 4,272,115 to Stock discloses a bumper system for a motor vehicle that includes a movable bumper beam. The bumper system has a superposed polyurethane molding covering the bumper beam. The bumper beam is comprised of a center metal section and two side metal sections, which are connected by spring-pivotal radius arms to the motor vehicle body. In the event of an impact involving the motor vehicle, the side sections pivot away from the motor vehicle body on their respective radius arms against the action of the associated springs to accommodate and redirect the impact force.
U.S. Pat. No. 3,694,018 to Levering discloses an elastomeric impact bumper assembly or system for dissipating energy during a collision. The bumper assembly includes a bumper beam that is connected to the rails of a motor vehicle body by elastomeric, impact energy dissipating bodies. The energy dissipating bodies are made of high-density polyurethane and have a generally rectangular, tubular configuration adapted to buckle under impact compression. The energy dissipating bodies are adapted to return to their original shape following the release of the impact energy.
Typically, the bumper systems described hereinabove include curved bumper beams for stylistic and aerodynamic considerations. Since these current bumper beams curve in one direction, considerable damage often occurs when the bumper system engages a body having an oppositely curved configuration, such as a telephone pole. In such a collision, the bumper beam and pole are curved in opposite orientations. This results in a line-contact impact, so that the impact force is localized along a line on the bumper beam. In current bumper systems, this situation is addressed by the use of load-spreading brackets which are added to the center of the bumper beam. Currently available designs known in the art are heavy and perform rather inefficiently, as well as being rather expensive to manufacture and attach to the bumper beam.